Dynamic address assignment for one-wire interface

Abstract

A method for identifying and assigning an address of a particular device is disclosed. The method includes discharging a capacitor in response to a first command from a host. A voltage of the discharged capacitor is then measured in response to a second command from the host. The address is assigned to the particular device when the voltage indicates that the particular device is an intended destination of the address.

What is claimed is:  
     
         1 . A method of identifying and assigning an address for a particular device connected to an interface, comprising: 
 discharging a capacitor in response to a first command from a host;    measuring a voltage of the discharged capacitor in response to a second command from the host; and    assigning the address to the particular device when the voltage indicates that the particular device is an intended destination of the address.    
     
     
         2 . The method of  claim 1 , further comprising: 
 charging a capacitor of a specified size.    
     
     
         3 . The method of  claim 2 , wherein the specified size of the capacitor is selected to provide a pre-determined level for the voltage of the discharged capacitor at the second command.  
     
     
         4 . The method of  claim 2 , wherein the specified size of the capacitor is selected to provide a unique time constant measured between the first command and the second command from the host.  
     
     
         5 . The method of  claim 2 , wherein said charging a capacitor includes charging the capacitor to a reference voltage.  
     
     
         6 . The method of  claim 1 , wherein the interface is a one-wire bus.  
     
     
         7 . The method of  claim 6 , wherein the one-wire bus is bi-directional.  
     
     
         8 . The method of  claim 1 , wherein said assigning the address includes receiving and writing the address to an address register.  
     
     
         9 . The method of  claim 1 , wherein said first command from a host includes a leading edge of an initiation pulse.  
     
     
         10 . The method of  claim 9 , wherein said second command from the host includes a trailing edge of the initiation pulse.  
     
     
         11 . The method of  claim 1 , wherein said measuring a voltage of the discharged capacitor includes comparing the voltage to a threshold voltage.  
     
     
         12 . The method of  claim 11 , wherein an indication that the destination of the address intended by the host is the particular device is determined by an outcome of said comparing the voltage of the discharged capacitor to a threshold voltage.  
     
     
         13 . The method of  claim 12 , wherein the outcome of said comparing includes the voltage being less than the threshold voltage.  
     
     
         14 . The method of  claim 12 , wherein the outcome of said comparing includes the voltage being greater than the threshold voltage.  
     
     
         15 . The method of  claim 14 , further comprising: 
 locking the particular device from further address assignment.    
     
     
         16 . The method of  claim 15 , wherein said locking includes placing the particular device into a state that disables acceptance of future first and second commands from the host so that other devices with smaller time constants may be identified and assigned.  
     
     
         17 . The method of  claim 1 , further comprising: 
 locking the particular device from further address assignment.    
     
     
         18 . A method for identifying and assigning a device address, comprising: 
 providing a combination of resistor and capacitor of selected sizes, said combination producing a particular time constant;    comparing the particular time constant to a threshold time; and    identifying and assigning the device address according to an outcome of said comparing.    
     
     
         19 . The method of  claim 18 , wherein the outcome provides that the particular time constant be greater than the threshold time.  
     
     
         20 . The method of  claim 18 , wherein the outcome provides that the particular time constant be less than the threshold time.  
     
     
         21 . An address identification and assignment system, comprising: 
 a combination of resistor and capacitor;    a voltage reference to provide a capacitor charge voltage and a threshold voltage;    a switching element to enable charging and discharging of the capacitor, where the capacitor is charged to the capacitor charge voltage; and    a comparator to compare voltage of the capacitor with the threshold voltage.    
     
     
         22 . The system of  claim 21 , further comprising: 
 a command interpreter to command the switching element to charge and discharge the capacitor in response to commands from a host, said command interpreter receiving a device address when a result signal from the comparator indicates that a current device is intended destination of the device address.    
     
     
         23 . The system of  claim 22 , further comprising: 
 an address register to store the device address.